1. Field of the Invention
The present invention relates to an image forming apparatus including a plurality of photosensitive bodies, and particularly, the present invention is suitable for an image forming apparatus including photosensitive bodies with different diameters.
2. Description of the Related Art
Conventionally, regular reflected light (return light noise) generated by perpendicular incidence (incident angle is zero) of a laser beam on a photosensitive surface is a problem when a light scanning apparatus scans on the photosensitive surface of a photosensitive body in an image forming apparatus. More specifically, the regular reflected light from the photosensitive surface of the photosensitive body returns to a laser light source through the same optical path as the incident optical path. The output of the laser light source becomes unstable, and the image is degraded. A configuration for solving the problem is known, wherein the laser beam from the laser light source enters at an angle relative to a surface normal line of the photosensitive surface of the photosensitive body, in a cross section (sub-scanning cross section) perpendicular to the main scanning direction.
To form a color image, an image forming apparatus including a plurality of photosensitive bodies (image bearing members) corresponding to the colors is known. Japanese Patent Application Laid-Open No. 2003-162122 discloses a configuration, wherein a plurality of photosensitive bodies is arranged on an arch, and incident angles of laser beams in the sub-scanning cross section are set to different angles in the photosensitive bodies.
The use frequency of the photosensitive body for black is generally the highest among the plurality of photosensitive bodies corresponding to the colors. Therefore, the diameter of the photosensitive body for black can be greater than the diameters of the other photosensitive bodies to increase the lifetime of the photosensitive body for black. The minimum value of the incident angle for avoiding the regular reflected light from returning to the laser light source depends on the diameter of the photosensitive body. Therefore, if the diameters of the photosensitive bodies are different, the incident angles of the laser beams relative to the photosensitive bodies need to be appropriately set.
However, all of the diameters of the photosensitive bodies are the same in the image forming apparatus described in Japanese Patent Application Laid-Open No. 2003-162122, and setting of appropriate incident angles for a plurality of photosensitive bodies with different diameters is not disclosed.